Twist drill and method for the production thereof

ABSTRACT

A twist drill includes a drill body having a chip flute extending a distance along the drill body. The chip flute has a leading edge and a run-out edge running along the chip flute. The run-out edge is disposed behind the leading edge in a direction of rotation of the twist drill. The chip flute, viewed cross-sectionally in a direction perpendicular to the longitudinal axis, includes a first wall portion and a second wall portion. The first wall portion extends along a curve between the run-out edge and the second wall portion. The second wall portion extends in a straight line from between the leading edge and the first wall portion. The first wall portion and the second wall portion are disposed adjoining one another and together define a J-shaped cross-sectional profile perpendicular to the longitudinal axis.

CONTINUING APPLICATION DATA

This application is a Continuation-In-Part application of InternationalPatent Application No. PCT/EP2007/008407, filed on Sep. 27, 2007, whichclaims priority from Federal Republic of Germany Patent Application No.10 2006 049 088.6, filed on Oct. 13, 2006. International PatentApplication No. PCT/EP2007/008407 was pending as of the filing date ofthis application. The United States was an elected state inInternational Patent Application No. PCT/EP2007/008407.

BACKGROUND

1. Technical Field

The present application relates to a drill and a method for theproduction thereof.

2. Background Information

Background information is for informational purposes only and does notnecessarily admit that subsequently mentioned information andpublications are prier art.

The present application relates to a modular drilling tool, comprising acarrier body and a cutting unit that can be fastened thereto, thecarrier body extending along a carrier body longitudinal axis, beingrealized substantially as a circular cylinder having a carrier bodyradius, and having a chip groove and a run-out or discharge edge thatextends along the chip groove. The present application furthermorerelates to a method for producing such a drilling tool.

Modular drilling tools are known in a variety of embodiments, whichdiffer, for example, in their holding of separately realized cuttingunits. For example, soldered-in hard-metal cutting tips or completedrill bits are used as cutting units. There are known, moreover,changeable cutting units, such as reversible cutting plates, which areheld on the carrier body of the drilling tool by means of screws, orsuch as cassettes, comprising reversible cutting plates, which areconnected to the carrier body through positive holding. There areadditionally known exchangeable drill bits, which are fastened to thecarrier body, for example, by means of screws or through clamping orthrough positive fit. Common to these modular drilling tools is thedivision into the cutting unit and the carrier body. The carrier bodyhas a front region, comprising chip grooves, and a shank region, forreceiving the drilling tool into a clamping device of a machine tool.

Some tools, realized as drilling tools having reversible cutting plates,inner chip grooves and outer chip grooves which are shaped in such a waythat they merge into one another in the middle to rear region of thetool. In the case of these tools, the chip groove has stiffening beadson both walls.

Fluctuations of the parameters in the drilling process result in theformation of differing chip shapes. In addition to the wanted fragmentalchip pieces, unwanted helical chips and helical fragmental chips canalso be produced. These chip portions, when being removed from thecutting edge of the drilling tool via the chip groove, continually orsubstantially continually cause contact with the wall of the bore,resulting in scores that impair the surface quality of the boreproduced.

Moreover, a continual or substantially continual occurrence is that, atthe run-out edge, chips become jammed between the wall of the bore andthe rear of the drill, and thereby cause increased torsional loading ofthe drill body. In this situation, there is also an increased thermalloading of the drill, since the heat produced during cutting is alsotaken away from the base of the bore with the chips. In extreme cases,such a jammed-in chip thereby becomes welded to the wall of the bore.

OBJECT OR OBJECTS

At least one object of the present application is to describe or definea modular drilling tool, and a method for the production thereof, havinga chip groove that is in one possible embodiment suitable in respect ofthe conveyance of chips.

SUMMARY

This object, in respect of the drilling tool, is achieved, according toat least one possible embodiment of the present application, by amodular drilling tool, comprising a carrier body and a cutting unit thatcan be fastened thereto. The carrier body extends along a carrier bodylongitudinal axis, and the body is realized substantially as a circularcylinder having a carrier body radius. The drilling tool furthercomprises a chip groove and a run-out or discharge edge that extendsalong the chip groove. The chip groove extends towards the run-out edgein a substantially convexly curved manner. A wall portion of the chipgroove that is opposite the run-out edge runs out rectilinearly suchthat—viewed in a cross sectional view perpendicular virtuallyperpendicular to the carrier body longitudinal axis—the chip groove isdelimited by a J-shaped chip groove wall and a concave fillet is formed,such that an acute advance angle is realized between a chip groovetangent to the run-out edge and a radial or radius that, at a tangentpoint, is tangential to the groove base in the region of the concavefillet. According to the latter, the drilling tool is realized in amodular manner, and has a substantially circular-cylindrical carrierbody having a carrier body radius, and has a holder, realized on thecarrier body, for the cutting unit. The carrier body comprises a run-outedge extending along a chip groove. The chip groove extends towards therun-out edge in a convexly curved manner such that—viewed in across-sectional view perpendicular or virtually perpendicular to thecarrier body longitudinal axis—a concave fillet is formed, and an acuteadvance angle is realized between a chip groove tangent to the run-outedge and a radial that, at a tangent point, is tangential to the groovebase in the region of the concave fillet. The delimiting wall of thechip groove in this case has a J-shaped contour, i.e. is composedapproximately of a semicircular arc, adjoining one side of which thereis a rectilinear wall portion. Overall, therefore, the chip groove hasan asymmetric conformation, to the extent that the chip groove has arectilinear wall portion on its one side and has a solely curved wallportion on its other side. The curved wall portion realizes the concavefillet and the acute advance angle. The rectilinearly extending wallportion is thus opposite the run-out edge in the direction of rotation,and extends out rectilinearly in the direction of the circumferentialsurface of the carrier body, said circumferential surface constituting arear of the drill. This enables the chip groove to be produced by simplybeing milled into the carrier body, along this rectilinear run-out.

In respect of production technology, therefore, the J-shaped form isachieved in that the grooves are made by means of a milling cutter, forexample a ball-ended milling cutter or a milling disc. The millingcutter is advanced is, not in the radial direction, but rathertangentially to the blank to be machined. Tangential advancing in thiscase is understood to mean that the center of the milling cutter is notapplied in the radial direction to the carrier body longitudinal axis,but rather that the center of the milling cutter is placed on the blanksuch that it is parallel or virtually parallel to, but at a distancefrom, a radial.

Chip groove tangent in this case is understood to be the tangent to thechip groove wall at the run-out corner at which the chip groove wallmeets the run-out edge, which tangent is oriented perpendicularly orvirtually perpendicularly in relation to the carrier body longitudinalaxis. The radial likewise extends perpendicularly or virtuallyperpendicularly in relation to the carrier body axis, and is tangentialto the chip groove wall in its lowest point, which here is denoted asthe tangent point.

The resultant sickle-shaped form of the chip cavity constituted by thechip groove results in an improved chip guidance, since, owing to theacute advance angle, there is realized a kind of wedge that, as it were,scrapes the chip from the wall of the bore. At the same time, owing tothe convex curvature and the concave fillet constituted thereby, thechip is guided securely into the chip groove, and held there. The riskof a chip becoming jammed between the drilling tool and the wall of thebore is therefore reduced. The curvature of the chip groove is alsoinstrumental in the shaping of the chip, such that the latter can betaken away easily and reliably in the chip groove. At the same time,owing to the J-shaped form, the chip is held reliably in the chipcavity.

According to an expedient development, the advance angle is in the rangeof between forty degrees and seventy degrees. A distinct and secure chipguidance within the chip groove is thereby achieved.

In at least one possible embodiment according to the presentapplication, in the region of the concave fillet the chip groove isrealized along a circular path having a radius of curvature. Such acircular path is produced, in one possible embodiment, by a millingcutter whose radius corresponds substantially to the radius of curvatureof the concave fillet. For reasons of production technology, the radiusof the concave fillet is somewhat greater than the radius of the millingcutter. The shape of the chip groove can thus be easily produced throughthe selection of a suitable tool, and the radius realized at this wallresults in an improved shaping of the chips to be taken away.

In one possible development, the chip groove has a diameter of between0.4 and 0.6 times the carrier body radius. In one possible embodiment ofthe present application, the remaining cross-section of the carrier bodyis, at the same time, suitable for absorbing the occurring forces andmoments.

In at least one possible embodiment, the concave fillet has a filletwidth of between 0.6 and 1 times the radius, and thus between 0.3 and0.5 times the diameter, of the milling cutter used. In one possibleembodiment, at the same time the concave fillet has a fillet depth inthe range of 0.3 to 0.8 times the radius of curvature. The fillet widthin this case is defined by the distance between the tangent point of thegroove base and the projection of the run-out edge to the radial. Thefillet depth in this case is the distance of the radial through thetangent point from the run-out edge. A concave fillet shaped thus guidesthe chips, over the entire course, in one possible embodiment well inthe chip groove cross-section.

In at least one possible embodiment, the carrier body has a front regionextending in the carrier body longitudinal direction, and has a run-outregion adjoining this front region. The run-out region serves to ejectthe chip material. In the run-out region, the advance angle decreases inthe carrier body longitudinal direction, in one possible embodimentcontinuously and progressively, towards the carrier body shank,resulting in a likewise continuously decreasing concave fillet. Owing tothis decrease in the concave fillet, the chip material can run freelyout of the groove. In this case, the advance angle decreases in thecarrier body longitudinal direction, from the end of the front region,beyond the run-out region, to at least zero degrees.

Owing to the greatness of their length relative to their diameter, andto the cross-section being reduced by the chip groove, drilling toolsare liable to deformations, including deflection, as a result of theforward-feed forces during the drilling operation. The vibrationsresulting therefrom reduce the quality of the bore. In a possibleembodiment, therefore, the run-out region has a length of between 1.0and 2.0 times the radius of curvature. This length essentially ensuresor promotes a free run-out of the chip material without excessiveelongation of the carrier body.

In one possible embodiment, in a middle partial region of the run-outregion the chip groove has opposing wall regions that extendparallelwise in the initial region and are connected by a semicircularpath. This groove shape can be easily produced by the milling cutterused for the front region.

The object relating to the production method is additionally achieved,according to the present application, by a method for producing amodular drilling tool, which has a carrier body realized substantiallyas a circular cylinder extending along a carrier body longitudinal axisand having a carrier body radius. The modular drilling tool comprises acutting unit that can be fastened to this carrier body, and also a chipgroove and a run-out edge that extends along the chip groove. The chipgroove is machined with the aid of a milling cutter such that—viewed ina cross-sectional view perpendicular or virtually to the carrier bodylongitudinal axis—the chip groove is realized to be J-shaped, such thatit extends towards the run-out edge in a convexly curved manner and aconcave fillet is formed. An acute advance angle is realized between achip groove tangent to the run-out edge and a radial that, at a tangentpoint, is tangential to the groove base in the region of the concavefillet. The possible embodiments stated in respect of the drilling toolare also to be assigned analogously to the method.

For the purpose of producing the drilling tool, provision is made inthis case whereby the chip groove is machined by means of a millingcutter in such a way that the chip groove, viewed in a cross-sectionalview perpendicular or virtually perpendicular to the carrier bodylongitudinal axis, extends convexly towards the run-out edge, and aconcave fillet is formed, in such a way that an acute advance angle isrealized between a chip groove tangent to the run-out edge and a radialthat, at a tangent point, is tangential to the groove base in the regionof the concave fillet. Such a method is suitable for producing the chipgroove in a continuous operation.

In one possible embodiment according to the present application, thechip groove is machined in a continuous operation, following the millingin the front region, in a run-out region adjoining the front region. Inthis case the milling cutter is in one possible embodiment swiveled insuch a way that the advance angle is reduced, in one possibleembodiment, to zero degrees. This measure results in the sickle-shapedform of the chip cavity, constituted by the concave fillet, undergoingtransition to a straight run-out. That is to say, at least in the endregion of the run-out region, the chip groove wall extends outrectilinearly, such that the chip can emerge easily from the chipgroove. In this case, the milling cutter is swiveled appropriately in asimple manner. There is then essentially no need or desire for toolchanging for alteration of the cross-sectional geometry, such that arapid, inexpensive realization of the chip groove in one working step isrendered possible.

The realization of the run-out region is also possible, in principle,independently of the form of the chip groove with the concave fillet. Arun-out region realized thus can also be used in the case ofconventional tools. Owing to the form of the run-out region,trouble-free emergence of chips from the chip groove is also achieved inthe case of these tools.

The above-discussed embodiments of the present invention will bedescribed further herein below. When the word “invention” or “embodimentof the invention” is used in this specification, the word “invention” or“embodiment of the invention” includes “inventions” or “embodiments ofthe invention”, that is the plural of “invention” or “embodiment of theinvention”. By stating “invention” or “embodiment of the invention”, theApplicant does not in any way admit that the present application doesnot include more than one patentably and non-obviously distinctinvention, and maintains that this application may include more than onepatentably and non-obviously distinct invention. The Applicant herebyasserts that the disclosure of this application may include more thanone invention, and, in the event that there is more than one invention,that these inventions may be patentable and non-obvious one with respectto the other.

BRIEF DESCRIPTION OF THE DRAWINGS

One possible embodiment of the present application is explained morefully in the following with reference to a drawing, wherein, inschematic representations, respectively:

FIG. 1 shows a perspective representation of a carrier body of a modulardrilling tool;

FIG. 2 shows a side view of the carrier body according to FIG. 1;

FIG. 3 shows a cross-section perpendicular or virtually perpendicular tothe carrier body longitudinal axis, along the section line III-III inFIG. 2:

FIG. 4 shows a top view of a section perpendicular or virtuallyperpendicular to the carrier body longitudinal axis, along the sectionline IV-IV in FIG. 2; and

FIG. 5 for the purpose of explaining the method for milling the chipgroove, shows a highly schematic front view of the carrier body with anindicated milling head in differing milling positions.

DESCRIPTION OF EMBODIMENT OR EMBODIMENTS

Parts that correspond to one another are denoted by the same referencesin the figures.

FIG. 1 shows a perspective view of a carrier body of a modular drillingtool 1, without a cutting unit. The carrier body 2 is divided into afront region 3 and a shank region 4. The two regions are separated by ashoulder 5, which constitutes a bearing-contact collar. In one possibleembodiment, the front region 3 has two chip grooves 6, which extendhelically, diametrically opposite one another, in the front region 3.Viewed in the direction of rotation D of the drill, the chip groove 6 isin each case adjoined at the end by a run-out edge 8, which likewiseextends helically, corresponding to the chip groove 6. Provided towardsthe shank region 4 is a run-out region 10, in which the chip groove 6runs out of the carrier body 2, along the shoulder 5. The carrier body 2additionally has a coolant bore 12 that corresponds, respectively, toeach of the chip grooves 6, the openings of which bores are arranged onthe end face 11 of the carrier body 2. In one embodiment, two plateseats 14, for receiving reversible cutting plates 16 (cf. FIG. 2), notrepresented in FIG. 1, are realized in the front end region of thecarrier body 2.

The reversible cutting plates 16 each constitute a cutting unit of themodular drilling tool 1. Exchangeable drill bits, in one possibleembodiment, can also be provided as cutting units, as an alternative toreversible cutting plates 16. The modular structure offers theinexpensive possibility of using for the cutting unit highly specializedmaterials that withstand the large loads during chip-removing machining,and at the same time of using other appropriate, and less expensive,materials for the carrier body. Owing to the exchangeability of thecutting units, it is also the case that the cutting units often need tobe exchanged or should be exchanged when cutting edges have become worn.

FIG. 2 shows a side view of the drilling tool 1. Represented on thecarrier body 2 are two reversible cutting plates 16, which are fastened,radially offset in relation to one another, in the respective plate seat14. The reversible cutting plates 16 project beyond the end face 11. Theradially inner reversible cutting plate 16 extends beyond the carrierbody longitudinal axis Z and at the same time overlaps the outerreversible cutting plate 16 in the radial direction, as a result ofwhich both reversible cutting plates 16 have an overlapping workingregion. If necessary and/or desired, the radially inner and radiallyouter reversible cutting plates 16 differ in their realization.

The length of the drilling tool 1 as a whole is given by a clampinglength L2 of the shank region 4 and an effective projection length L1.The run-out region 10 adjoining the front region 3 has the length L3. Inthis case, the active drilling length of the front region 3 correspondsto a bore depth for which the drilling tool is intended. This bore depthis usually specified in multiples of the carrier body diameter. Theactive length of the front region corresponds substantially to thedifference between the effective projection length L1 and the length L3of the run-out region 10.

Whereas, over the length of the front region 3, the chip groove 6 has achip groove geometry that remains substantially constant, this geometryvaries continuously or substantially continuously in the course of therun-out region 10. Substantially constant geometry in this case isunderstood to mean that the basic geometry, explained in the followingwith reference to FIG. 3, is maintained apart from possible variationsof the individual dimensions, for example because of a core tapering inthe longitudinal direction of the drilling tool 1. The chip groove 6 inthe front region 3 in this case is realized for good chip shaping andchip discharge, in one possible embodiment in such a way that the chipis held securely in the chip groove 6 and the chip is prevented,restricted, and/or minimized from becoming jammed between a wall of thebore and the rear of the drill. In the run-out region 10, by contrast,the chip groove 6 is realized such that the chip can emerge easily fromthe chip groove 6.

FIG. 3 shows a cross-sectional surface along the section line III-IIIaccording to FIG. 2. The two coolant bores 12 are arranged within thecarrier body 2, which has a carrier body radius T_(r). The chip groove 6is delimited by an approximately J-shaped chip groove wall 17. Thelatter has a wall portion that has the shape of a circular arc and has aradius r. This wall portion in the shape of a circular arc runs out, onthe one side, to the rear of the drill, and adjoins the run-out edge 8.

The chip groove 6 thereby constitutes a concave fillet 18 towards therun-out edge 8, and has a sickle-shaped course in the region of theconcave fillet 18. The sickle tip is constituted by the run-out edge 8.An advance angle W is realized in this case between a chip groovetangent T and a radial or radius R. The chip groove tangent T is thetangent of the circular-arc-shaped wall portion, in the run-out point ofthe wall portion, to the run-out edge 8. The radial R is constituted bya straight line that extends through the middle point (carrier bodylongitudinal axis Z) and that is tangential to the groove base in theregion of the concave fillet. The point of contact of the radial R inthe region of the groove base is termed the tangent point P. The concavefillet 18 has a fillet depth H and a fillet width B. The fillet depth His defined as the distance of the radial R from the run-out edge 8, i.e.the fillet depth H—viewed in a cross-sectional view—corresponds to theshortest distance between the radial R and the run-out edge 8, thus tothe corner point between the chip groove wall and the rear of the drill.The fillet width B in this case is defined by the distance between theradial R tangential to the groove base and a projection of the run-outedge to the radial R. The fillet width B is therefore the distancebetween the tangent point P and a vertical to the radial R extendingthrough the corner point (run-out edge 8) between the chip groove walland the rear of the drill.

The chip groove wall runs out acutely towards the run-out edge 8, suchthat an approximately wedge-shaped wall region is realized. The advanceangle W in this case lies in a range of between approximately fortydegrees and seventy degrees. This very acute form reliably reduces therisk of a chip becoming jammed between a bore wall and the rear of thedrill. Rather, owing to the wedge-shaped or sickle-shaped form, the chipis scraped from the bore wall and caught in the sickle-shaped concavefillet 18. At the same time, a good chip shaping effect is achieved bythe curvature of the chip groove wall adjoining the run-out edge 8. Forthis purpose, the concave fillet 18 has a radius of curvature that, inone possible embodiment, is in the range of between 0.4 and 0.6 timesthe carrier body radius T_(r). In order to hold the chip securely andreliably in the chip groove 6, the concave fillet width B isapproximately in the range of between 0.6 and 1.0 times the radius ofcurvature r. At the same time, the concave fillet depth H isapproximately 0.3 to 0.8 times the radius of curvature r. Overall,reliable chip removal is achieved through this chip groove geometry.

The wall portion 19 of the chip groove 6 that is opposite the run-outedge 8 in the direction of rotation D is of little importance for theshaping and the removal of chips, and in one possible embodiment it isrealized as a straight wall portion 19. Starting from the run-out edge 8above the circular-arc-shaped wall portion in the region of the concavefillet 18, the straight wall portion 19 extends as far as the rear ofthe drill of the carrier body 2.

The chip groove geometry described here can be produced in a simple andinexpensive manner, in one possible embodiment in a single-stagemachining process, with the aid of a milling cutter, in one possibleembodiment a ball-ended milling cutter. There is often no need or desirefor resource-intensive grinding processes or multiple application of amachining tool. Rather, the chip groove geometry is determinedsubstantially by the geometry of a milling head 20 (cf. FIG. 5) of theball-ended milling cutter. The radius of curvature r of the concavefillet 18 therefore also corresponds substantially to the radius of theball-ended milling cutter.

The geometry of the chip groove 6 in the run-out region 10 can be seenfrom FIG. 4. Whereas the basic geometry, shown in FIG. 3, with theconcave fillet 18 and the wall portion 19 running out rectilinearlyopposite the run-out edge 8, is constant or substantially constantbeyond the front region 3, the geometry varies over the run-out region10, in one possible embodiment continuously or substantiallycontinuously.

The chip groove 6 is widened in the run-out region 10 and shaped outinto the shoulder 5. In the run-out region 10, the fillet depth Hdecreases progressively, until finally a rectilinear run-out is realizedat the end of the run-out region 10. The advance angle W is thereforereduced to zero degrees, and in certain instances can also assumenegative values. The chip is therefore no longer held captive in thechip groove 6, but can emerge from the latter without difficulty.

A concave fillet is now realized at the end of the run-out region 10, onthe opposite wall portion 19, and the wall portion 19 extends along acurved line having the radius of curvature r.

This geometry in the run-out region 10 is easily produced through adefined swiveling of the milling cutter. The milling method forproducing the chip groove 6 is explained with reference to FIG. 5, inwhich differing positions of the milling head 20 of a ball-ended millingcutter, which are denoted by K1-K7, can be seen. The milling head 20 hasa radius that corresponds to the radius of curvature r. The carrier bodylongitudinal axis Z constitutes the z direction, and the plane of thedrawing constitutes the x-y plane of the indicated coordinate system.

For the production of the carrier body 2, a suitable round material isturned to the required or desired outer dimension prior to the machiningoperation represented in FIG. 5. In this process, a shoulder 5 isproduced between the portion of the carrier body 2 intended as a frontregion 3 and that intended as a shank region 4. A thus producedsemi-finished product for a carrier body 2 is clamped-in by the shankregion for the purpose of milling the chip grooves 6, such that thefront region 3 to be produced can be machined. By means of the millinghead 20, milling into the carrier body 2 is effected as described in thefollowing, such that a chip groove 6, having the required or desiredgeometric characteristics, is produced for each machining operation.

For this purpose, starting from the end face of the carrier body 2, themilling head 20 is used to mill into the latter, the distance of themilling cutter longitudinal axis 24 from the carrier body longitudinalaxis Z being less than the carrier body radius T_(r), until the millinghead 20 is tangential to a core circle 22 of the carrier body 2. In thisposition (K1), the milling head 20 is moved, in a forward-feed motion inthe z direction, towards the shank region 4. At the same time, thecarrier body 2 is rotated in the direction of rotation D, such that thehelical chip groove 6 is realized with a constant or substantiallyconstant pitch and constant or substantially constant advance angle W.The thus produced front region 3 of the chip groove 6 has a length thatcorresponds to the drilling depth intended for the drilling tool 1.During the machining of the front region 3, the milling head 20 assumesthe relative position denoted by K1 in FIG. 5 in respect of the carrierbody 2.

The special movements of the milling head 20 or of the carrier body 1that are described here correspond to the possible and easily controlledsequence of movements. The movements can also be executed, however,through appropriate control of the respectively other part. What iscrucial is the relative positioning and movement of the milling head 20in relation to the carrier body 2.

For the purpose of producing the chip groove 6 in the run-out region 10the milling head 20, with its longitudinal axis 24 in the xy plane, isrotated about Z in a previously calculated manner. The milling head 20is therefore, as it were, rolled on the core circle 22. For thispurpose, the milling head 20 is rotated about an axis of rotation 26oriented parallelwise in relation to the z direction. At the same time,a forward feed is effected in the z direction and the carrier body 2 isrotated further in the direction of rotation D. The milling head 20thereby moves through the positions K1 to K7. The depth of the chipgroove 6 remains unchanged in this case.

Whereas, in the position K1, the milling cutter longitudinal axis 24 isoriented parallelwise in relation to a center plane 28 of the carrierbody 2, in a middle region of the run-out region 10 it is orientedperpendicularly or virtually perpendicularly relative to the centerplane 28 (approximately position K4), and at the end of the run-outregion 10 it encloses an obtuse angle of approximately one hundred sixtydegrees in relation to the center plane 28 (position K7). In onepossible embodiment, the center plane 28 is defined by a plane that isoriented parallelwise in relation to the rectilinearly extending wallportion 19 at the end of the front region 3 and at the start of therun-out region 10.

From the position K7, the milling head 20 is moved, in the direction ofits longitudinal axis 24, out of the carrier body 2. The machiningoperation is thereby concluded.

In at least one possible embodiment, the drilling tool is a twist drillhaving a longitudinal axis Z and a substantially circular cylindricalshape. The drill has a shank portion 4 that is configured to be insertedinto and held by a machine tool, and has a drill body that is connectedto the shank portion 4. The drill body also has a tip portion oppositethe shank portion 4 with at least two cutting inserts or plates 16removably fastened to the drill body at the tip portion. In at least onepossible embodiment, at least two coolant channels 12 run through theshank portion 4 and the drill body to at least two coolant channelopenings in the tip portion. The drill body also has at least twohelical chip flutes 6 and at least two land surfaces corresponding tothe chip flutes 6. Each of the chip flutes comprises a leading edge 8and a trailing edge, each of which edge is disposed immediately adjacentand to extend along the length of its corresponding land surface. Theleading edge 8 is disposed ahead of its corresponding land surface inthe direction of rotation D of the twist drill, while the trailing edgeis disposed behind its corresponding land surface in the direction ofrotation D. Each chip flute also comprises a chip-guiding section 3 anda chip-discharge section 10. The chip-guiding section 3 is locatedbetween the at least two cutting inserts and the chip-discharge section10. The chip-guiding section 3 comprises a first wall portion 18 and asecond wall portion 19. The first wall portion 18 of the chip-guidingsection 3 is disposed to extend along a curve from the leading edge 8toward a central portion of the twist drill. The first wall portion 18of the chip-guiding section 3 also is located between the leading edge 8and the second wall portion 19 of the chip-guiding section The firstwall portion 18 of the chip-guiding section 3 and its corresponding landsurface meet at the leading edge 8, and define an acute angle therebetween at the leading edge 8. The first wall portion of thechip-guiding section 3 has a concave cross-sectional profileperpendicular to the longitudinal axis Z. This concave design promotesthe retaining of chips produced in a cutting process in the chip flutes6 to minimize contact of chips with a wall of a hole being cut by thetwist drill, and to minimize torque forces and jamming of the twistdrill in a hole being cut by the twist drill and to thus minimize damageto the surface texture of a wall of a hole being cut by the twist drill.The second wall portion 19 of the chip-guiding section 3 extends in astraight line from the trailing edge toward a central portion of thetwist drill. The second wall portion 19 of the chip-guiding section 3 islocated between the trailing edge and the first wall portion 18 of thechip-guiding section 3. The first wall portion 18 of the chip-guidingsection 3 and the second wall portion 19 of the chip-guiding section 3adjoin one another and together define a J-shaped cross-sectionalprofile perpendicular to the longitudinal axis Z. The chip-dischargesection 10 also comprises a first wall portion 18 and a second wallportion 19. The first wall portion 18 of the chip-discharge section 10extends in a straight line from the leading edge 8 toward a centralportion of the twist drill. The first wall portion 18 of thechip-discharge section 10 is disposed between the leading edge 8 and thesecond wall portion 19 of the chip-discharge section 10. The first wallportion 18 of the chip-discharge section 10 has a straightcross-sectional profile perpendicular to the longitudinal axis Z, thedesign of which promotes evacuation of chips produced in a cuttingprocess and received from the chip-guiding section 3. The second wallportion 19 of the chip-discharge section 10 extends along a curve fromthe trailing edge toward a central portion of the twist drill. Thesecond wall portion 19 of the chip-discharge section 10 is locatedbetween the trailing edge and the first wall portion 18 of thechip-discharge section 10. The second wall portion 19 of thechip-discharge section 10 has a concave cross-sectional profileperpendicular to the longitudinal axis Z configured to promoteevacuation of chips produced in a cutting process and received from thechip-guiding section 3. The first wall portion 18 of the chip-guidingsection 3 has a curvature such that an acute angle is formed between afirst line T and a second line. The first line T is tangential to thefirst wall portion 18 of the chip-guiding section 3 at the leading edge8. The second line R extends radially from the longitudinal axis Z, andis also perpendicular to a third line extending along and from thestraight second wall portion 19 of the chip-guiding section 3 andintersecting with the second line R, and finally is also tangential tothe first wall portion 18 of the chip-guiding section 3 at, the tangentpoint P.

Modular drilling tool 1 having a carrier body 2 and a cutting unit 16that is attachable thereto, the carrier body 2 extending along a carrierbody longitudinal axis Z, being realized substantially as a circularcylinder having a carrier body radius and having a chip groove 6 and arun-out edge 8 that extends along the chip groove 6, the chip groove 6extending towards the run-out edge 8 in a convexly curved manner suchthat—viewed in a cross-sectional view perpendicular or virtuallyperpendicular to the carrier body longitudinal axis Z—a J-shaped chipgroove 6 having a concave fillet 18 is formed, and an acute advanceangle W is realized between a chip groove tangent T to the run-out edge8 and a radial R that, at a tangent point P, is tangential to the groovebase in the region of the concave fillet 18, thereby resulting inimproved chip guidance in the chip groove.

One feature or aspect of an embodiment is believed at the time of thefiling of this patent application to possibly reside broadly in amodular drilling tool 1, comprising a carrier body 2 and a cutting unit16 that can be fastened thereto, the carrier body 2 extending along acarrier body longitudinal axis 7, being realized substantially as acircular cylinder having a carrier body radius T_(r), and having a chipgroove 6 and a run-out edge 8 that extends along the chip groove,wherein the chip groove 6 extends towards the run-out edge 8 in aconvexly curved manner and a wall portion 19 of the chip groove 6 thatis opposite the run-out edge 8 runs out rectilinearly such that—viewedin a cross sectional view perpendicular or virtually perpendicular tothe carrier body longitudinal axis Z—the chip groove 6 is delimited by aJ-shaped chip groove wall 17 and a concave fillet 18 is formed, suchthat an acute advance angle W is realized between a chip groove tangentT to the run-out edge 8 and a radial R that, at a tangent point P, istangential to the groove base in the region of the concave fillet.

Another feature or aspect of an embodiment is believed at the time ofthe filing of this patent application to possibly reside broadly in themodular drilling tool 1, wherein the advance angle W is between aboutforty degrees and about seventy degrees.

Yet another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly inthe modular drilling tool 1, wherein the chip groove 6 in the region onthe concave fillet 18 extends along a circular path having a radius ofcurvature r.

Still another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly inthe modular drilling tool 1, wherein the radius of curvature r isapproximately between 0.4 and 0.6 times the carrier body radius T_(r).

A further feature or aspect of an embodiment is believed at the time ofthe filing of this patent application to possibly reside broadly in themodular drilling tool 1, wherein the concave fillet has a fillet width Bthat is approximately between 0.6 and 1.0 times the radius of curvaturer and that is defined by the distance between the tangent point P and aprojection of the run-out edge 8 to the radial R.

Another feature or aspect of an embodiment is believed at the time ofthe filing of this patent application to possibly reside broadly in themodular drilling tool 1, wherein the concave fillet has a fillet depth Happroximately in the range of 0.3 to 0.8 times the radius of curvaturer, the fillet depth H being defined by the distance between the run-outedge 8 and the radial R.

Yet another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly inthe modular drilling tool 1, wherein the carrier body 2 has a frontregion 3 extending in the direction of the carrier body longitudinalaxis Z and has a run-out region 10 adjoining the front region, theadvance angle W decreasing continuously in the direction of the carrierbody longitudinal axis Z in the run-out region 10.

Still another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly inthe modular drilling tool 1 wherein the advance angle W decreases to atleast zero degrees in the run-out region 10.

A further feature or aspect of an embodiment is believed at the time ofthe filing of this patent application to possibly reside broadly in themodular drilling tool 1, wherein the run-out region 10 has a length ofbetween 1.0 and 2.0 times the radius of curvature r.

One feature or aspect of an embodiment is believed at the time of thefiling of this patent application to possibly reside broadly in themodular drilling tool 1, wherein, in an end region of the run-out region10, the region that is opposite the run-out edge 8 extends rectilinearlyand the wall portion that extends towards the run-out edge extends in aconvexly curved manner.

Another feature or aspect of an embodiment is believed at the time ofthe filing of this patent application to possibly reside broadly in themodular drilling tool 1, wherein in a middle partial region of therun-out region 10 the chip groove 6 has opposing wall portions, runningoutwards rectilinearly, which, in one possible embodiment, are parallelor virtually parallel in relation to one another and are intermediatelyconnected via a circular path.

Yet another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly in amethod for producing a modular drilling tool 1, which has a carrier body2 realized substantially as a circular cylinder extending along acarrier body longitudinal axis Z and having a carrier body radius r, andwhich has a cutting unit 16 that can be fastened to this carrier body,and has a chip groove 6 and a run-out edge 8 that extends along the chipgroove 6, the chip groove 6 being machined with the aid of a millingcutter such that—viewed in a cross-sectional view perpendicular orperpendicular to the carrier body longitudinal axis Z—the chip groove 6is realized to be J-shaped, such that it extends towards the run-outedge 8 in a convexly curved manner and a concave fillet is formed, suchthat an acute advance angle W is realized between a chip groove tangentT to the run-out edge 8 and a radial R that, at a tangent point P, istangential to the groove base in the region of the concave fillet.

Still another feature or aspect of an embodiment is believed at the timeof the filing of this patent application to possibly reside broadly inthe method, the milling cutter being swiveled-in in a run-out region 10of the chip groove 6 in such a way that the advance angle W decreases inthe direction of the carrier body longitudinal axis Z.

The components disclosed in the various publications, disclosed orincorporated by reference herein, may possibly be used in possibleembodiments of the present invention, as well as equivalents thereof.

The purpose of the statements about the technical field is generally toenable the Patent and Trademark Office and the public to determinequickly, from a cursory inspection, the nature of this patentapplication. The description of the technical field is believed, at thetime of the filing of this patent application, to adequately describethe technical field of this patent application. However, the descriptionof the technical field may not be completely applicable to the claims asoriginally filed in this patent application, as amended duringprosecution of this patent application, and as ultimately allowed in anypatent issuing from this patent application. Therefore, any statementsmade relating to the technical field are not intended to limit theclaims in any manner and should not be interpreted as limiting theclaims in any manner.

The appended drawings in their entirety, including all dimensions,proportions and/or shapes in at least one embodiment of the invention,are accurate and are hereby included by reference into thisspecification.

The background information is believed, at the time of the filing ofthis patent application, to adequately provide background informationfor this patent application. However, the background information may notbe completely applicable to the claims as originally filed in thispatent application, as amended during prosecution of this patentapplication, and as ultimately allowed in any patent issuing from thispatent application. Therefore, any statements made relating to thebackground information are not intended to limit the claims in anymanner and should not be interpreted as limiting the claims in anymanner.

All, or substantially all, of the components and methods of the variousembodiments may be used with at least one embodiment or all of theembodiments, if more than one embodiment is described herein.

The purpose of the statements about the object or objects is generallyto enable the Patent and Trademark Office and the public to determinequickly, from a cursory inspection, the nature of this patentapplication. The description of the object or objects is believed, atthe time of the filing of this patent application, to adequatelydescribe the object or objects of this patent application. However, thedescription of the object or objects may not be completely applicable tothe claims as originally filed in this patent application, as amendedduring prosecution of this patent application, and as ultimately allowedin any patent issuing from this patent application. Therefore, anystatements made relating to the object or objects are not intended tolimit the claims in any manner and should not be interpreted as limitingthe claims in any manner.

All of the patents, patent applications and publications recited herein,and in the Declaration attached hereto, are hereby incorporated byreference as if set forth in their entirety herein.

The summary is believed, at the time of the filing of this patentapplication, to adequately summarize this patent application. However,portions or all of the information contained in the summary may not becompletely applicable to the claims as originally filed in this patentapplication, as amended during prosecution of this patent application,and as ultimately allowed in any patent issuing from this patentapplication. Therefore, any statements made relating to the summary arenot intended to limit the claims in any manner and should not beinterpreted as limiting the claims in any manner.

It will be understood that the examples of patents, published patentapplications, and other documents which are included in this applicationand which are referred to in paragraphs which state “Some examples of .. . which may possibly be used in at least one possible embodiment ofthe present application . . . ” may possibly not be used or useable inany one or more embodiments of the application.

The sentence immediately above relates to patents, published patentapplications and other documents either incorporated by reference or notincorporated by reference.

Some examples of drills, cutting tools, and components thereof, that maypossibly be utilized or adapted for use in at least one possibleembodiment may possibly be found in the following U.S. Pat. Nos.7,390,148, entitled “Boring tool and a cutting insert therefor”; No.7,364,390, entitled “Drilling tool” No. 7,360,974, entitled “Rotarycutting tool, such as a drill, comprising an exchangeable cuttinginsert, and an exchangeable cutting insert”; No. 7,322,777, entitled“Reamer with clamping arrangement for adjusting cutting insert and othercutting tools with clamping arrangements for adjusting cutting inserts”;No. 7,322,774, entitled “End mill and a method of operating an endmill”; No. 7,313,991, entitled “Cutting insert and use thereof”; No.7,311,481, entitled “Milling cutter”; No. 7,201,543, entitled “Twistdrill and method for producing a twist drill which method includesforming a flute of a twist drill”; No. 7,168,512, entitled “Cuttinginsert and milling cutter with such a cutting insert”; No. 7,090,447,entitled “Twist drill for drilling with a countersink cuttingarrangement, and a cutting tool with a countersink cutting arrangement,and a cutting-chamfering tool”; No. 7,077,606, entitled “Rotating chipremoving tool, such as a drilling and chamfering tool, with cuttinginserts, and a milling cutter with cutting inserts”; No. 7,070,367,entitled “Twist drill for drilling having a replaceable drill tip, and areplaceable drill tip for use in a twist drill”; No. 7,048,480, entitled“Twist drill with a replaceable cutting insert and a rotary cutting toolwith a replaceable cutting insert”; No. 6,988,859, entitled “Drill bitand method for grinding a drill bit”; No. 6,929,434, entitled “Rotarycutting tool”; No. 6,688,817, entitled “Drill for drilling, a method formaking a drill for drilling, and a cutting tool”; No. 6,676,339,entitled “Indexable cutting insert for machining workpieces”; No.6,655,882, entitled “Twist drill having a sintered cemented carbidebody, and like tools, and use thereof”; No. 6,374,712, entitled “Diskmilling cutter and suitable indexable insert” No. 6,309,149, entitled“Twist drill for dry drilling”; No. 6,293,738, entitled “Thread cuttingbit”; No. 6,231,276, entitled “Cutting tool with an insertableadjustable stop, and an adjustable stop for a cutting tool”; No.6,164,879, entitled “Drilling tool for drilling in solid metal”; No.6,142,485, entitled “Chuck for rotary tools”; No. 6,116,825, entitled“Rotating cutting tool with a coolant passage and a method of providingit with coolant”; No. 5,967,710, entitled “Drilling tool for drilling insolid metal”; No. 5,873,683, entitled “Boring tool”; and No. 5,300,100,entitled “Drilling tool with reset inserts”.

The following patents, patent applications or patent publications, arehereby incorporated by reference as if set forth in their entiretyherein: DE 195 22 836 A1 having the following English translation theGerman title “DRILLING TOOL,” published on Jan. 2, 1997.

All of the patents, patent applications or patent publications, whichwere cited in the International Search Report dated Mar. 11, 2008,and/or cited elsewhere are hereby incorporated by reference as if setforth in their entirety herein as follows: GB 1,338,586, having thetitle “ROCK DRILL”, published on Nov. 28, 1973;“STUFENWERKZEUGE-NACHSHARGEN AUF FINER CNC-SCHLEIFMASCHINE,” vol. 121,no. 12, published on Dec. 1, 1988, and having International StandardSerial Number 0043-2792; DE 43 38 545, having the following Englishtranslation of the German title “DRILL BIT, PARTIC. FOR WOODMATERIAL—HAS CYLINDRICAL SHAPE WITH BASIC CUTTING EDGE AND HAS STRAIGHTSWARF GROOVE EXTENDING TO CENTRE OF BIT,” published on Mar. 24, 1994;U.S. Pat. No. 3,836,278, having the title “tapered drill bit,” publishedon Sep. 17, 1974; SU 715 238, having inventors Yarosiav V. KUNTSYAK,published on Feb. 15, 1980; U.S. Pat. No. 5,685,673, having the title“TWIST DRILL WITH REVERSE FLUTES,” published on Nov. 11, 1997; WO84/00910, having the title “MICRO DRILL,” published on Mar. 15, 1884; EP0750960, having the title following English translation of the Germantitle “DRILLING TOOL, PARTICULARLY FOR METALLIC MATERIALS,” published onJan. 2, 1997; “METAL-CUTTING TOOLS TECHNOLOGICAL MODIFICATION OF THETWIST DRILL CHIP GROOVE PROFILE,” vol. 20, no. 12, published in 2002,having International Standard Serial Number 1068-798X; and DE 41 15 030,having the following English translation of the German title“CYLINDRICAL BIT,” published Jun. 25, 1992.

The purpose of incorporating U.S. patents, Foreign patents,publications, etc. is solely to provide additional information relatingto technical features of one or more embodiments, which information maynot be completely disclosed in the wording in the pages of thisapplication. Words relating to the opinions and judgments of the authorand not directly relating to the technical details of the description ofthe embodiments therein are not incorporated by reference. The wordsall, always, absolutely, consistently, preferably, guarantee,particularly, constantly, ensure, necessarily, immediately, endlessly,avoid, exactly, continually, expediently, need, must, only, perpetual,precise, perfect, require, requisite, simultaneous, total, unavoidable,and unnecessary, or words substantially equivalent to theabove-mentioned words in this sentence, when not used to describetechnical features of one or more embodiments, are not considered to beincorporated by reference herein.

The corresponding foreign and international patent publicationapplications, namely, Federal Republic of Germany Patent Application No.10 2006 049 088.6, filed on Oct. 13, 2006, having inventor Peter KarlMERGENTHALER, and DE-OS 10 2006 049 088.6 and 10 2006 049 088.6, andInternational Application No. PCT/EP2007/008407, filed on Sep. 27, 2007,having WIPO Publication No. WO 2008/046496 and inventor Peter KarlMERGENTHALER, are hereby incorporated by reference as if set forth intheir entirety herein for the purpose of correcting and explaining anypossible misinterpretations of the English translation thereof. Inaddition, the published equivalents of the above corresponding foreignand international patent publication applications, and other equivalentsor corresponding applications, if any, in corresponding cases in theFederal Republic of Germany and elsewhere, and the references anddocuments cited in any of the documents cited herein, such as thepatents, patent applications and publications, are hereby incorporatedby reference as if set forth in their entirety herein.

The purpose of incorporating the Foreign equivalent patent applicationPCT/EP2007/008407 and German Patent Application 10 2006 049 088.6 issolely for the purpose of providing a basis of correction of any wordingin the pages of the present application, which may have beenmistranslated or misinterpreted by the translator. Words relating toopinions and judgments of the author and not directly relating to thetechnical details of the description of the embodiments therein are notto be incorporated by reference. The words all, always, absolutely,consistently, preferably, guarantee, particularly, constantly, ensure,necessarily, immediately, endlessly, avoid, exactly, continually,expediently, need, must, only, perpetual, precise, perfect, require,requisite, simultaneous, total, unavoidable, and unnecessary, or wordssubstantially equivalent to the above-mentioned word in this sentence,when not used to describe technical features of one or more embodiments,are not generally considered to be incorporated by reference herein.

Statements made in the original foreign patent applications PCTEP2007/008407 and DE 10 2006 049 088.6 from which this patentapplication claims priority which do not have to do with the correctionof the translation in this patent application are not to be included inthis patent application in the incorporation by reference.

All of the references and documents, cited in any of the documents citedherein, are hereby incorporated by reference as if set forth in theirentirety herein. All of the documents cited herein, referred to in theimmediately preceding sentence, include all of the patents, patentapplications and publications cited anywhere in the present application.

The description of the embodiment or embodiments is believed, at thetime of the filing of this patent application, to adequately describethe embodiment or embodiments of this patent application. However,portions of the description of the embodiment or embodiments may not becompletely applicable to the claims as originally filed in this patentapplication, as amended during prosecution of this patent application,and as ultimately allowed in any patent issuing from this patentapplication. Therefore, any statements made relating to the embodimentor embodiments are not intended to limit the claims in any manner andshould not be interpreted as limiting the claims in any manner.

The details in the patents, patent applications and publications may beconsidered to be incorporable, at applicant's option, into the claimsduring prosecution as further limitations in the claims to patentablydistinguish any amended claims from any applied prior art.

The purpose of the title of this patent application is generally toenable the Patent and Trademark Office and the public to determinequickly, from a cursory inspection, the nature of this patentapplication. The title is believed, at the time of the filing of thispatent application, to adequately reflect the general nature of thispatent application. However, the title may not be completely applicableto the technical field, the object or objects, the summary, thedescription of the embodiment or embodiments, and the claims asoriginally filed in this patent application, as amended duringprosecution of this patent application, and as ultimately allowed in anypatent issuing from this patent application. Therefore, the title is notintended to limit the claims in any manner and should not be interpretedas limiting the claims in any manner.

The abstract of the disclosure is submitted herewith as required by 37C.F.R. §1.72(b). As stated in 37 C.F.R. §1.72(b):

-   -   A brief abstract of the technical disclosure in the        specification must commence on a separate sheet, preferably        following the claims, under the heading “Abstract of the        Disclosure.” The purpose of the abstract is to enable the Patent        and Trademark Office and the public generally to determine        quickly from a cursory inspection the nature and gist of the        technical disclosure. The abstract shall not be used for        interpreting the scope of the claims.        Therefore, any statements made relating to the abstract are not        intended to limit the claims in any manner and should not be        interpreted as limiting the claims in any manner.

The embodiments of the invention described herein above in the contextof the preferred embodiments are not to be taken as limiting theembodiments of the invention to a of the provided details thereof, sincemodifications and variations thereof may be made without departing fromthe spirit and scope of the embodiments of the invention.

What is claimed is: 1-20. (canceled)
 21. A twist drill comprising: adrill body of generally cylindrical shape disposed about a longitudinalaxis, the drill body having a first end configured to be coupled to amachine tool and an opposite second end, the drill body including a chipflute formed therein, the chip flute extending a distance along thedrill body, the chip flute having a leading edge and a run-out edgerunning along the chip flute, the run-out edge disposed behind theleading edge in a direction of rotation of the twist drill, wherein: thechip flute, viewed cross-sectionally in a direction perpendicular to thelongitudinal axis, includes a first wall portion and a second wallportion, the first wall portion extends along a curve between therun-out edge and the second wall portion, the second wall portionextends in a straight line from between the leading edge and the firstwall portion, the first wall portion and the second wall portion aredisposed adjoining one another and together define a J-shapedcross-sectional profile perpendicular to the longitudinal axis, and thefirst wall portion has a curvature such that an acute advance angle isformed between a first line and a second line, the first line beingtangential to the first wall portion at the run-out edge and the secondline extending: radially from the longitudinal axis and perpendicularlyto a third line extending along and from the second wall portion andintersecting with the second line, and tangentially to the first wallportion.
 22. The twist drill of claim 21 wherein the acute advance angleis between 40 degrees and 70 degrees.
 23. The twist drill of claim 21wherein the first wall extends along a circular path having a constantradius of curvature.
 24. The twist drill of claim 21 wherein the radiusof curvature is in the range of from about 0.4 to about 0.6 times theradius of the drill body.
 25. The twist drill of claim 21 wherein adistance between a fourth line and fifth line, which fourth line extendsperpendicular to the second line at the point where the second line istangential to the first wall portion, and which fifth line extendsperpendicular to the second line and through the run-out edge, is in therange of from about 0.6 and about 1.0 times the radius of curvature. 26.The twist drill of claim 21 wherein the first wall portion has a depthwhich is defined by a distance between the second line and a sixth lineextending from the run-out edge parallel to the second line, whichdistance is approximately in the range of 0.3 to 0.8 times the radius ofcurvature.
 27. The twist drill of claim 21 wherein the acute advanceangle decreases moving from the second end toward the first end of thedrill body.
 28. The twist drill of claim 27 wherein the acute advanceangle decreases to at least 0 degrees in a run-out region.
 29. The twistdrill of claim 28 wherein the first wall extends along a circular pathhaving a constant radius of curvature and wherein the run-out region hasa length, along the longitudinal axis of the drill body, in the range offrom about 1.0 to about 2.0 times the radius of curvature.
 30. The twistdrill of claim 21 wherein the opposite second end of the drill bodyincludes a plate seat configured to receive a cutting plate therein. 31.The twist drill of claim 30 further comprising a cutting plate at leastpartially disposed in the plate seat and removably fastened to the drillbody.
 32. A method for producing a twist drill body of generallycylindrical shape disposed about a longitudinal axis; the drill bodyhaving a first end configured to be coupled to a machine tool and anopposite second end; the drill body including a chip flute formedtherein; the chip flute extending a distance along the drill body; thechip flute having a leading edge and a run-out edge running along thechip flute; the run-out edge disposed behind the leading edge in adirection of rotation of the twist drill; the chip flute, viewedcross-sectionally in a direction perpendicular to the longitudinal axis,having a first wall portion and a second wall portion; the first wallportion extending along a curve between the run-out edge and the secondwall portion; the second wall portion extending in a straight line frombetween the leading edge and the first wall portion; the first wallportion and the second wall portion adjoining one another and togetherdefining a J-shaped cross-sectional profile perpendicular to thelongitudinal axis; and the first wall portion having a curvature suchthat an acute advance angle is formed between a first line and a secondline, the first line being tangential to the first wall portion at therun-out edge and the second line extending: radially from thelongitudinal axis and perpendicularly to a third line extending alongand from the second wall portion and intersecting with the second line,and tangentially to the first wall portion; the method comprising:milling the chip flute using a milling cutter by swiveling the millingcutter head in a run-out region of the chip flute such that the advanceangle decreases moving in a direction from the second end of the drillbody toward the first end of the drill body.